KR102536664B1 - Multi-junction photovoltaic device - Google Patents

Abstract

A multi-junction photovoltaic device is provided comprising a first sub-cell disposed over a second sub-cell, the first sub-cell comprising a photoactive region comprising a layer of perovskite material, 2 sub-cells contain silicon heterojunctions (SHJ).

Description

Multi-junction photovoltaic device

The present invention is directed to a monolithic integrated perovskite-on-silicon multijunction photovoltaic device that exceeds the efficiency of the bottom silicon sub-cell in a unijunction structure and produces a net gain in power conversion efficiency. it's about

Over the past 40 years, there has been growing awareness of the need to replace fossil fuels with safer, more sustainable energy sources. In addition, the new energy supply must have low environmental impact, high efficiency, ease of use, and cost-effective production. To this end, solar energy is seen as one of the most promising technologies, but the high costs of manufacturing devices that capture solar energy, including high material costs, have historically hampered widespread use of solar energy.

All solids have their own characteristic energy-band structure that determines a wide range of electrical properties. Electrons can transition from one energy band to another, but each transition requires a specific minimum energy, and the amount of energy required varies from material to material. Electrons get the energy they need for the transition by absorbing phonons (heat) or photons (light). The term “band gap” refers to the range of energy differences in a solid in which no electronic state can exist, and generally refers to the difference in energy (in electron volts) between the top of the valence band and the bottom of the conduction band. The efficiency of a material used in a photovoltaic device, such as a solar cell, under normal sunlight conditions is a function of the band gap for that material. If the band gap is too high, most solar photons cannot be absorbed, if it is too low, most photons will have far more energy than needed to excite electrons across the band gap, and the rest will be wasted. The Shockley-Quiser limit means the theoretical maximum amount of electrical energy that can be extracted per photon of incident light, and is about 1.34 eV. The focus of much recent research on photovoltaic devices has been the search for materials with band gaps as close as possible to this maximum.

One class of photovoltaic materials that has attracted considerable attention are perovskites. This type of material forms the ABX ₃ crystal structure, which has been found to exhibit favorable band gaps, high absorption coefficients and long diffusion lengths, making these compounds ideal absorbers in photovoltaic devices. An early example of the use of perovskite materials in photovoltaic applications is Kojima, A. et al. (2009. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. Journal of the American Chemical Society, 131(17), pp. 6050-1), where hybrid organic-inorganic metal halide perovskites were used as photosensitizers in liquid electrolyte-based photoelectrochemical cells. Kojima et al. reported obtaining the highest solar energy conversion efficiency (or power energy conversion efficiency, PCE) of 3.8%, but in this system the perovskite absorber decays rapidly and the cell degrades after only 10 minutes. .

Subsequently, Lee, MM et al. (2012. Efficient hybrid solar cells based on meso-superstructured organometal halide perovskites. Science (New York, NY), 338(6107), pp.643-7) described a liquid electrolyte as a solid-state hole conductor reported a “meso-superstructured solar cell” replaced by spiro-MeOTAD (or hole-transporting material, HTM). Lee et al reported a significant improvement in cell stability as a result of avoiding the use of liquid solvents while reporting a significant increase in conversion efficiency achieved. In the described example, CH ₃ NH ₃ PbI ₃ perovskite nanoparticles act as photosensitizers in photovoltaic cells, inject electrons into mesoscopic TiO ₂ scaffolds, and holes into solid-state HTMs. do. Both TiO ₂ and HTM serve as selective contacts, through which charge carriers generated by photoexcitation of perovskite nanoparticles are extracted.

Further research described in WO2013/171517 discloses a way to obtain more stable and highly efficient photovoltaic devices by using mixed anionic perovskites as photosensitizers/absorbers in photovoltaic devices instead of mono-anionic perovskites did In particular, this document discloses that the superior stability of mixed anionic perovskites is highlighted by finding that the device exhibits a full solar power conversion efficiency in excess of 10% while exhibiting negligible color bleaching during the device manufacturing process. there is. In comparison, equivalent single-anion perovskites are relatively unstable, and bleaching occurs rapidly when preparing films from single halide perovskites at ambient conditions.

More recently, WO2014/045021 describes a planar heterojunction type (PHJ) photovoltaic device comprising a thin film of a photoactive perovskite absorber disposed between an n-type (electron transport) layer and a p-type (hole transport) layer. described. Unexpectedly, it has been found that superior device efficiency can be obtained by using compact (i.e. effective/no open pore) thin films of photoactive perovskites, contrary to the requirements of mesoporous composites, and perovskite absorbers have been shown to simplify It was shown that the device architecture can function with high efficiency.

Some of the recent work on the application of perovskites in photovoltaic devices has explored the potential of these materials to improve the performance of conventional silicon-based solar cells by combining them with perovskite-based cells in tandem/multijunction arrays. has been focused on In this regard, a multijunction photovoltaic device is a plurality of distinct sub-cells (i.e., each having its own photoactive area) that are stacked together and convert more of the solar spectrum into electricity, increasing the overall efficiency of the device. includes To do so, each photoactive region of each sub-cell is selected to ensure that the photoactive region's band gap efficiently absorbs photons from a particular segment of the solar spectrum. This has two important advantages over conventional unijunction photovoltaic devices. First, the combination of multiple sub-cells/photoactive regions and different band gaps ensures that a wider range of incident photons can be absorbed by the multi-junction device, and second, each sub-cell/photoactive region has a different band gap within a relevant portion of the spectrum. It is more effective in extracting energy from photons. In particular, the lowest band gap of a multijunction photovoltaic device will be lower than that of a typical unijunction device, so that a multijunction device can absorb photons with less energy than can be absorbed by a unijunction device. . Moreover, for photons absorbed by both the multi-junction and mono-junction devices, the multi-junction device will absorb these photons more efficiently since the band gap closer to the photon energy reduces heat loss.

In a multi-junction type device, the uppermost sub-cell/photoactive region within the stack has the highest band gap, and the band gap of the lower sub-cell/photoactive region decreases towards the bottom of the device. This configuration maximizes photon energy extraction as the top sub-cell/photoactive region absorbs the highest energy photons while allowing transmission of photons with lower energies. Each subsequent sub-cell/photoactive region then minimizes degradation losses by extracting energy from photons closest to its band gap. The bottom sub-cell/photoactive region absorbs all remaining photons with energies above its band gap. Therefore, when designing a multijunction cell, it is important to select a sub-cell with a photoactive region with the correct bandgap to optimize the harvesting of the solar spectrum. In this regard, for a tandem photovoltaic device comprising two sub-cells/photoactive regions, an uppermost sub-cell/photoactive region and a lowermost sub-cell/photoactive region, the lowermost sub-cell/photoactive region ideally has a ratio of about 1.1 eV, and the top sub-cell/photoactive region should ideally have a band gap of about 1.7 eV (Coutts, T.J., Emery, K. a. & Scott Ward, J., 2002. Modeled performance of polycrystalline thin-film tandem solar cells. Progress in Photovoltaics: Research and Applications, 10(3), pp.195203).

As a result, hybrid organic-halide compositions for use in tandem photovoltaic devices can be obtained where the band gap of these perovskite materials can be tuned from about 1.5 eV to greater than 2 eV by changing the halide composition of the organometal halide perovskite. There has been interest in the development of inorganic perovskite solar cells (Noh, J.H. et al., 2013. Chemical Management for Colourful, Efficient, and Stable Inorganic-Organic Hybrid Nanostructured Solar Cells. Nano letters, 2, pp.2831) . In particular, it is possible to tune the band gap of an organometal halide perovskite to about 1.7 eV by changing the halide composition, which when combined with a crystalline silicon lowermost sub-cell having a band gap of about 1.12 eV is a tandem. Ideal for use as the uppermost sub-cell of a structure.

In this regard, Schneider, BW et al. (Schneider, BW et al., 2014. Pyramidal surface textures for light trapping and antireflection in perovskite-on-silicon tandem solar cells. Optics Express, 22(S6), p.A1422) modeled reported on the modeling of a perovskite-on-silicon tandem cell with a four-terminal mechanical layered structure. Loeper, P. et al. (Loeper, P. et al., 2015. Organic-inorganic halide perovskite/crystalline silicon four-terminal tandem solar cells. Physical chemistry chemical physics: PCCP, 17, p.1619) reported that crystalline silicon heterojunction Embodiments of a 4-terminal tandem solar cell consisting of a top sub-cell of methyl ammonium lead triiodide (CH ₃ NH ₃ PbI ₃ ) (ie organometallic halide perovskite) mechanically layered on a bottom sub-cell. reported about. Similarly, Bailie, C. et al. (Bailie, C. et al., 2015. Semi-transparent perovskite solar cells for tandems with silicon and CIGS. Energy Environ. Sci., pp.128) reported copper indium gallium diselenide ( reported on a mechanically stacked tandem embodiment consisting of a top sub-cell of methyl ammonium lead triiodide (CH ₃ NH ₃ PbI ₃ ) on a bottom sub-cell of CIGS or low-grade polycrystalline silicon. Methyl _ammonium lead _triiodide ( _{CH 3 NH} reported on simulations of both mechanically stacked (4-terminal) and monolithically integrated (2-terminal) tandem _devices consisting of a 3 PbI 3 ₎ top sub-cell and a crystalline silicon bottom sub-cell. Next, Mailoa, JP et al. (Mailoa, JP et al., 2015. A 2-terminal perovskite/silicon multi-junction solar cell enabled by a silicon tunnel junction. Applied Physics Letters, 106(12), p.121105) The fabrication of an integrated tandem solar cell consisting of an ammonium lead triiodide (CH ₃ NH ₃ PbI ₃ ) top sub-cell and a crystalline silicon bottom sub-cell is reported.

In a mechanically stacked multi-junction photovoltaic device, individual sub-cells are stacked by polymerizing each other, and each has its own separate electrical contact, so that the individual sub-cells are connected in parallel, and current matching is unnecessary. This contrasts with monolithically integrated multijunction photovoltaic devices, where individual sub-cells are electrically connected in series between a single pair of terminals, requiring recombination layers or tunnel junctions and current matching between adjacent sub-cells. do. Mechanically stacked multijunction photovoltaic devices do not require current matching between sub-cells, but the additional size and cost of additional contacts and substrates, and the lower practical efficiency limit, make the mechanically stacked structure an integrally integrated structure. makes it less advantageous.

So far, the only example of a monolithically integrated perovskite-on-silicon multijunction photovoltaic device has produced a net loss in power conversion efficiency compared to the efficiency of the bottom silicon sub-cell in a monojunction structure. . In this regard, Mailoa, J.P. reported a two-terminal perovskite-on-silicon multijunction photovoltaic device, where the efficiency of a monojunction silicon cell is 13.8% and the maximum efficiency reported for a two-terminal multijunction device is 13.7%. am.

The inventors have developed an integrally integrated perovskite-on-silicon multijunction photovoltaic device that exceeds the efficiency of the bottom silicon sub-cell in a unijunction structure to produce a net gain in power conversion efficiency.

The multi-junction type photovoltaic device according to the first aspect,

a first sub-cell disposed on a second sub-cell;

The first sub-cell comprises an n-type region comprising one or more n-type layers, a p-type region comprising one or more p-type layers, and disposed between the n-type region and the p-type region, and the n-type region and a photoactive region comprising a layer of perovskite material, without open pores, forming a planar heterojunction with one or both of the p-type regions;

The perovskite material has the general formula (IA),

A _x A' _{1 - x} B(X _y X' _1-y ) ₃ (IA)

where A is a formamidinium cation (FA), A ^' is a cesium cation (Cs ⁺ ), B is Pb ²⁺ , X is an iodide, X' is a bromide, and 0 < x ≤ 1 , 0 < y ≤ 1,

The second sub-cell includes a silicon heterojunction (SHJ).

A surface of the second sub-cell adjacent to the first sub-cell may be textured with a surface profile having a roughness average (R _a ) of less than 500 nm.

The surface of the second sub-cell adjacent to the first sub-cell preferably has a roughness average (R _a ) of 50 to 450 nm. In a preferred embodiment, the surface of the second sub-cell adjacent to the first sub-cell has a roughness average (R _a ) of 100 to 400 nm, more preferably a roughness average (R _a ) of 200 nm to 400 nm. have

A surface of the second sub-cell adjacent to the first sub-cell may have a root mean square roughness (R _rms ) of 50 nm or less. The surface of the second sub-cell adjacent to the first sub-cell may have a peak-to-peak roughness (R _t ) of 100 nm to 400 nm, preferably about 250 nm. The surface of the second sub-cell adjacent to the first sub-cell may have an average peak-to-peak spacing (S _m ) of 10 μm to 50 μm, preferably about 25 μm.

Optionally, a surface of the second sub-cell adjacent to the first sub-cell has an undulating profile.

The layer of perovskite material is preferably disposed as a substantially continuous and conformal layer on a surface conformal to the adjacent surface of the second sub-cell.

The device may further include an intermediate region disposed between and connecting the first sub-cell and the second sub-cell, and the intermediate region includes one or more interconnection layers. Preferably each of the one or more interconnect layers includes a transparent conductive material. Preferably, each of the one or more interconnection layers has an average transmittance of 90% or more for near and infrared rays and a sheet resistance (Rs) of 200 ohms/square (Ω/sq) or less. The intermediate region may include an interconnection layer made of indium tin oxide (ITO), preferably the layer of ITO has a thickness of 10 nm to 60 nm.

The photoactive region of the first sub-cell may include a layer of perovskite material without open pores. The photoactive region of the first sub-cell may further comprise an n-type region comprising one or more n-type layers and a p-type region comprising one or more p-type layers, wherein the layer of perovskite material is an n-type region. It is placed between the region and the p-type region. The layer of perovskite material may form a planar heterojunction having one or both of an n-type region and a p-type region.

The n-type region may include an n-type layer including an inorganic n-type material. Inorganic n-type materials include oxides of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or oxides of mixtures of two or more of the foregoing metals; sulfides of cadmium, tin, copper, zinc or sulfides of mixtures of two or more of the foregoing metals; selenide of cadmium, zinc, indium, gallium or a selenide of a mixture of two or more of the foregoing metals; and tellurides of cadmium, zinc, cadmium or tin, or tellurides of mixtures of two or more of the foregoing metals. The n-type region may include an n-type layer comprising TiO ₂ , preferably the n-type layer is a compact layer of TiO ₂ .

The n-type region may include an n-type layer comprising an organic n-type material. The organic n-type material is fullerene or fullerene derivative, perylene or perylene derivative, or poly{[N,N0-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide) -2,6-diyl] -alt-5,50-(2,20-bithiophene)} (P(NDI2OD-T2)).

The n-type region may include an n-type layer having a thickness of 20 nm to 40 nm, more preferably 30 nm. Optionally, the n-type region consists of an n-type layer with a thickness of 20 nm to 40 nm, more preferably 30 nm.

The p-type region may include a p-type layer comprising an inorganic p-type material. Inorganic p-type materials include oxides of nickel, vanadium, copper or molybdenum; and CuI, CuBr, CuSCN, Cu ₂ O, CuO or CIS.

The p-type region may include a p-type layer comprising an organic p-type material. The organic p-type material may be selected from any one of Spiro-MeOTAD, P3HT, PCPDTBT, PVK, PEDOT-TMA, and PEDOT:PSS, and preferably the p-type region consists of a p-type layer containing spiro-MeOTAD.

The p-type region may include a p-type layer having a thickness of 200 nm to 300 nm, more preferably 250 nm. Optionally, the p-type region consists of a p-type layer with a thickness of 200 nm to 300 nm, more preferably 250 nm.

The n-type region may be adjacent to the second sub-cell.

The device may further include a first electrode and a second electrode, wherein the first sub-cell and the second sub-cell are disposed between the first electrode and the second electrode, and the first sub-cell is disposed between the first electrode and the second electrode. contact the electrode. The first electrode may contact the p-type region of the first sub-cell.

The first electrode may include a transparent or translucent electrically conductive material. The first electrode is a material having a sheet resistance (Rs) of 50 ohms/square (Ω/sq) or less and an average transmittance of greater than 90% for visible and infrared light, preferably greater than 95% for visible and infrared light. can be made with The first electrode may consist of a layer of indium tin oxide (ITO), preferably the layer of ITO has a thickness of 100 nm to 200 nm, more preferably 150 nm.

The photoactive region of the first sub-cell may comprise a layer of perovskite material having a band gap between 1.50 eV and 1.75 eV, preferably between 1.65 eV and 1.70 eV.

The second sub-cell may include a bifacial sub-cell, then the device further includes a third sub-cell disposed below the second sub-cell, the third sub-cell comprising perovskite A photoactive region comprising a layer of material. The photoactive region of the third sub-cell may include a layer of perovskite material that is the same as or different from the perovskite material of the photoactive region of the first sub-cell. The first sub-cell may have a normal structure, then the third sub-cell may have an inverted structure.

A surface of the second sub-cell adjacent to the third sub-cell may have a root mean square roughness (R _rms ) of 50 nm or less. A surface of the second sub-cell adjacent to the third sub-cell may have a peak-to-peak roughness (R _t ) of 100 nm to 400 nm, preferably 250 nm. A surface of the second sub-cell adjacent to the third sub-cell may have an average peak-to-peak spacing (S _m ) of 10 μm to 50 μm, preferably 25 μm. A surface of the second sub-cell adjacent to the third sub-cell may have an undulating profile. The layer of perovskite material of the third sub-cell is then disposed as a substantially continuous and conformal layer on a surface conformal to the adjacent surface of the second sub-cell.

The device may further include an additional intermediate region disposed between and connecting the third sub-cell and the second sub-cell, the additional intermediate region comprising one or more additional interconnection layers. Preferably each of the one or more additional interconnection layers is made of a transparent conductor material. Each of the one or more additional interconnect layers may have an average transmittance of 90% or greater for near and infrared light and a sheet resistance (Rs) of 200 ohms/square (Ω/sq) or less. The intermediate region may include an additional interconnection layer made of indium tin oxide (ITO), preferably the layer of ITO has a thickness of 10 nm to 60 nm.

The photoactive region of the third sub-cell may further comprise an n-type region comprising one or more n-type layers and a p-type region comprising one or more p-type layers, wherein the layer of perovskite material is an n-type region. It is placed between the region and the p-type region. The p-type region of the third sub-cell may be adjacent to the second sub-cell.

A third sub-cell may be disposed between the first electrode and the second electrode, and the third sub-cell contacts the second electrode. The second electrode may then contact the n-type region of the photoactive region of the third sub-cell.

The second electrode may include a transparent or translucent electrically conductive material. The second electrode is a material having a sheet resistance (Rs) of 50 ohms/square (Ω/sq) or less and an average transmittance of greater than 90% for visible and infrared light, preferably greater than 95% for visible and infrared light. can be made with The second electrode may consist of a layer of indium tin oxide (ITO), preferably the layer of ITO has a thickness of 100 nm to 200 nm, more preferably 150 nm.

The photoactive region of the third sub-cell may comprise a layer of perovskite material having a band gap between 1.50 eV and 1.75 eV, preferably between 1.65 eV and 1.70 eV.

also a photoactive region comprising a layer of organic charge transport material; and a layer of transparent conducting oxide (TCO) material deposited on the layer of organic charge transport material. The layer of TCO material has a sheet resistance (Rs) of 50 ohms per square (Ω/sq) or less and an average transmittance of greater than 90% for visible and infrared light, preferably greater than 95% for visible and infrared light. . The layer of TCO material may have an amorphous structure.

The photoactive region may include a photoactive perovskite material, and then a layer of organic charge transport material may be disposed on top of the photoactive perovskite material. The organic charge transport material may be either an n-type material or a p-type material.

According to a third aspect a method of manufacturing a photovoltaic device is provided. The method includes depositing a layer of an organic charge transport material, and depositing a layer of a transparent conductive oxide (TCO) material on the organic charge transport material using a remote plasma sputtering process.

The plasma directed to the sputtering target by the remote plasma sputtering process may have a density of 10 ¹¹ ions ^{cm -3} to 5 x 10 ¹³ ions cm ^-3 . Ions in the plasma may have an energy of 30 eV to 50 eV. The step of depositing the layer of TCO can be carried out at a temperature of less than 100 ^° C. The method does not include annealing the deposited layer of TCO at a temperature above 200 ^° C.

The photovoltaic device can include a photoactive region comprising a layer of organic charge transport material and a layer of photoactive perovskite material, and then depositing the layer of organic charge transport material comprises a layer of photoactive perovskite material. depositing a layer of organic charge transport material on it.

Also provided is a multi-junction photovoltaic device comprising a first sub-cell disposed over a second sub-cell, the first sub-cell comprising a photoactive region comprising a layer of perovskite material; , where the surface of the second sub-cell adjacent to the first sub-cell has a root mean square roughness (R _rms ) of 50 nm or less.

The surface of the second sub-cell adjacent to the first sub-cell may have a peak-to-peak roughness (R _t ) of 100 nm to 400 nm, preferably about 250 nm. The surface of the second sub-cell adjacent to the first sub-cell may have an average peak-to-peak spacing (S _m ) of 10 μm to 50 μm, preferably about 25 μm. A surface of the second sub-cell adjacent to the first sub-cell may have an undulating profile. The layer of perovskite material may be disposed as a substantially continuous and conformal layer on a surface conformal to an adjacent surface of the second sub-cell.

Hereinafter, an example of the present invention will be described in more detail with reference to the accompanying drawings.

1 schematically illustrates an integrally integrated multijunction photovoltaic device comprising a top perovskite-based sub-cell and a bottom silicon heterojunction (SHJ) sub-cell;
2 schematically illustrates one embodiment of a silicon heterojunction (SHJ) sub-cell;
3A schematically depicts one embodiment of a perovskite-based sub-cell with an ultra-thin absorber (ETA) cell architecture;
3B schematically illustrates one embodiment of a perovskite-based sub-cell with a meso-superstructured solar cell (MSSC) architecture;
3C schematically depicts one embodiment of a perovskite-based sub-cell with a planar heterojunction device architecture;
3D schematically illustrates one embodiment of a perovskite-based sub-cell in which the perovskite forms a bulk heterojunction with a semiconductor porous scaffold material;
FIG. 3E schematically depicts one embodiment of a perovskite-based sub-cell without an HTM in which the perovskite forms a bulk heterojunction with the semiconductor porous scaffold material;
3F schematically depicts one embodiment of a perovskite-based sub-cell in which the perovskite forms a bulk heterojunction with an insulating porous scaffold material;
4 schematically illustrates one embodiment of the integrally integrated multi-junction photovoltaic device of FIG. 1;
5 schematically illustrates one embodiment of a surface profile of a second sub-cell of an integrally integrated multi-junction photovoltaic device;
6 schematically illustrates a double-sided, integrally integrated, multi-junction photovoltaic device;
FIG. 7 schematically illustrates one embodiment of the double-sided integrally integrated multi-junction photovoltaic device of FIG. 6;
8 and 9 show IV curves and calculated device characteristics of an embodiment of an n-type crystalline silicon heterojunction (SHJ) sub-cell;
10 and 11 are IV curves and calculated device characteristics for a multi-junction device including a perovskite-based sub-cell integrally integrated on an n-type crystalline silicon heterojunction (SHJ) sub-cell, respectively. shows

Justice

As used herein, the term “photoactive” refers to a region, layer or material capable of photoelectrically responding to light. Thus, a photoactive region, layer or material can generate electricity by absorbing energy carried by photons in the light (eg, by creating electron-hole pairs or excitons).

As used herein, the term “perovskite” refers to a material having a three-dimensional crystal structure related to that of CaTiO ₃ or a material comprising a layer of material having a structure related to that of CaTiO ₃ . The structure of CaTiO ₃ can be represented by the formula ABX ₃ , where A and B are cations of different sizes and X is an anion. In the unit cell, the A cation is located at (0,0,0), the B cation is located at (1/2, 1/2, 1/2), and the X anion is located at (1/2, 1/2, 0) located in Generally, the A cation is larger than the B cation. A person skilled in the art will know that when A, B and X are varied, the structure of the perovskite material may be distorted from the structure adopted by CaTiO ₃ to a distorted structure of lower symmetry due to the different ionic sizes. Symmetry will also be lower if the material includes a layer with a structure related to that of CaTiO ₃ . Materials comprising layers of perovskite materials are well known. For example, the structure of a material employing a structure of the K ₂ NiF ₄ type includes a layer of perovskite material. A person skilled in the art knows that perovskite materials can be represented by the formula [A][B][X] ₃ , where [A] is one or more cations, [B] is one or more cations and [X] is one or more anions. You will know. When the perovskite contains two or more A cations, different A cations may be regularly or irregularly distributed over the A site. When the perovskite contains two or more B cations, different B cations may be regularly or irregularly distributed over the B site. When the perovskite contains two or more X anions, different X anions can be regularly or irregularly distributed over the X sites. The symmetry of perovskites containing two or more A cations, two or more B cations, or two or more X cations is often lower than that of CaTiO ₃ .

As noted in the previous paragraph, the term "perovskite" as used herein refers to (a) a material having a three-dimensional crystal structure related to that of CaTiO ₃ , or (b) a material comprising layers of material. , wherein the layer has a structure related to that of CaTiO3. Both of these two categories of perovskites can be used in the device according to the present invention, but in some cases perovskites of the first category (a), i.e. perovskites with a three-dimensional (3D) crystal structure It is preferable to use Typically these perovskites contain a 3D network of perovskite unit lattices with no separation between the layers. On the other hand, the second category of perovskites (b) includes perovskites with a two-dimensional (2D) layered structure. Perovskites with a 2D layered structure may contain layers of perovskite unit cells separated by (intercalated) molecules and an example of such a 2D layered perovskite is [2-(1-cyclohexenyl )ethylammonium] ₂ PbBr ₄ . 2D layered perovskites tend to have high exciton binding energies, which favor the generation of bound electron-hole pairs (excitons) over free charge carriers under photoexcitation. The bound electron-hole pairs cannot move far enough to reach the p-type or n-type contact, where they can transfer (ionize) and create free charge. Consequently, in order to generate free charge, the exciton binding energy must be overcome, which represents an energy cost for the charge generation process, resulting in low voltage and low efficiency in photovoltaic cells. In contrast, perovskites with a 3D crystal structure tend to have much lower exciton binding energies (similar to thermal energies) and thus can generate free carriers immediately after photoexcitation. Accordingly, it is preferred that the perovskite semiconductors employed in the devices and processes of the present invention are perovskites of the first category (a), i.e., perovskites having a 3D crystal structure. This is particularly advantageous when the optoelectronic device is a photovoltaic device.

The perovskite material employed in the present invention is a material capable of absorbing light and thereby generating free charge carriers. Therefore, the perovskite employed is a light absorbing perovskite material. However, one skilled in the art will appreciate that the perovskite material can be a perovskite material capable of emitting light by accepting the charge of both electrons and holes, which then recombine and emit light. Thus, the employed perovskite may be a light-emitting perovskite.

As will be appreciated by those skilled in the art, the perovskite material employed in the present invention may be a perovskite that functions as an n-type electron transport semiconductor when light-doped. Alternatively, it may be a perovskite that acts as a p-type hole transporting semiconductor when light-doped. Thus, perovskites can be n-type or p-type, or intrinsic semiconductors. In a preferred embodiment, the perovskite employed is one that acts as an n-type electron transport semiconductor when light-doped. Perovskite materials can exhibit bipolar charge conductivity and thus act as n-type semiconductors and p-type semiconductors. In particular, a perovskite can act as both an n-type semiconductor and a p-type semiconductor depending on the type of junction formed between the perovskite and an adjacent material.

Typically, the perovskite semiconductor used in the present invention is a photosensitive material, that is, a material capable of both photogeneration and charge transport.

As used herein, the term “mixed anion” refers to a compound containing two or more different anions. The term “halide” refers to an element selected from Group 17 of the Periodic Table of Elements, ie the anion of a halogen. Typically, halide anion means fluoride anion, chloride anion, bromide anion, iodide anion or astatide anion.

As used herein, the term “metal halide perovskite” refers to a perovskite whose chemical formula includes at least one metal cation and at least one halide anion. As used herein, the term "organometal halide perovskite" refers to a metal halide perovskite whose formula contains one or more organic cations.

The term "organic material" has its normal meaning in the art. Typically, an organic material means a material comprising one or more compounds containing carbon atoms. As will be appreciated by those skilled in the art, organic compounds are covalently bonded to another carbon atom, or a hydrogen atom, or a halogen atom, or a chalcogen atom (eg, an oxygen atom, a sulfur atom, a selenium atom, or a tellurium atom). may contain carbon atoms. Those skilled in the art will understand that the term "organic compound" typically does not include compounds that are primarily ionic, such as carbides, for example.

The term "organic cation" means a cation comprising carbon. Cations may contain additional elements, for example, cations may include hydrogen, nitrogen or oxygen. The term "inorganic cation" means a cation that is not an organic cation. Basically, the term "inorganic cation" means a cation that does not contain carbon.

As used herein, the term "semiconductor" refers to a material having an electrical conductivity intermediate between that of a conductor and a dielectric. The semiconductor may be an n-type semiconductor, a p-type semiconductor or an intrinsic semiconductor.

As used herein, the term “dielectric” refers to a material that is an electrical insulator or very poor conductor of current. The term dielectric therefore excludes semiconductor materials such as titania. As used herein, the term dielectric typically refers to a material having a band gap of 4.0 eV or greater (the band gap of titania is about 3.2 eV).

As used herein, the term "n-type" refers to a region, layer or material comprising an extrinsic semiconductor in which the concentration of electrons is greater than that of holes. Therefore, in an n-type semiconductor, electrons are majority carriers and vacancies are minority carriers, and thus it is an electron transport material. Accordingly, the term "n-type region" as used herein refers to a region of one or more electron transporting (ie, n-type) materials. Similarly the term "n-type layer" refers to a layer of electron transport (ie n-type) material. The electron transporting (ie, n-type) material can be a single electron transporting compound or elemental material, or a mixture of two or more electron transporting compounds or elemental materials. The electron transport compound or elemental material may be undoped or doped with one or more dopant elements.

As used herein, the term “p-type” refers to a region, layer or material comprising an extrinsic semiconductor in which the concentration of holes is greater than that of electrons. In a p-type semiconductor, holes are the majority carriers and electrons are the minority carriers, so it is a hole transport material. Therefore, the term “p-type region” as used herein refers to a region of one or more hole transporting (ie, p-type) materials. Similarly the term “p-type layer” means a layer of hole transporting (ie p-type) material. The hole transporting (ie, p-type) material can be a single hole transporting compound or elemental material, or a mixture of two or more hole transporting compounds or elemental materials. The hole transport compound or elemental material may be undoped or doped with one or more dopant elements.

As used herein, the term “band gap” refers to the energy difference between the top of the valence band and the bottom of the conduction band within a material. One skilled in the art can readily measure the band gap of a material without undue experimentation.

As used herein, the term “layer” refers to any structure in the form of a sheet (e.g., extending substantially in two perpendicular directions but limiting extension in a third vertical direction). may have a thickness that varies throughout. Typically, the layer has an approximately constant thickness. As used herein, "thickness" of a layer means the average thickness of the layer. The thickness of the layer can be readily measured, for example, by using a microscopy method such as electron microscopy of a cross-section of the film, or by protometry using, for example, a stylus profilometer.

As used herein, the term "porous material" refers to a material in which pores are arranged. Thus, for example, in a porous material, voids are the volumes where there is no material within a body of material. Individual pores may be of the same size or of different sizes. The size of the pores is defined as "pore size". For most phenomena involving porous solids, the limiting size of a pore is the limiting size of the smallest dimension referred to as the width of a pore in the absence of any additional precision (i.e., the width of a slit-shaped pore, the size of a cylindrical or spherical pore). diameter, etc). When comparing cylindrical and slit pores, the diameter of the cylindrical pores should be used as their "pore width" to avoid misleading variations (Rouquerol, J. et al, (1994) Recommendations for the characterization of Porous solids (Technical Report. Pure and Applied Chemistry, 66(8)). The following classification and definition have been adopted in the previous IUPAC literature (J. Haber. (1991) Manual on catalyst characterization (Recommendations 1991). Pure and Applied Chemistry.): A micropore is a width smaller than 2 nm (i.e., pore size). has; The mesopores have a width (ie, pore size) of 2 nm to 50 nm; The macropores have a width (ie pore size) greater than 50 nm. Nanopores can also be considered to have a width (ie, pore size) of less than 1 nm.

Voids within a material may include open as well as "closed" voids. Closed voids are voids that are unconnected cavities in a material, ie, voids that are isolated within the material, not connected to any other voids, and thus inaccessible to fluids exposed to the material. On the other hand, "open pores" are accessible to these fluids. The concepts of open and closed pores are discussed in detail in J. Rouquerol et al.

Thus, open porosity means the fraction of the total volume of a porous material in which fluid flow can effectively occur. Therefore, it excludes closed voids. The term "open voids" is interchangeable with the terms "connected voids" and "effective voids" and is abbreviated to simply "voids" in the art. Therefore, the term “free of open pores” as used herein means that there are no effective pores. Accordingly, materials without open pores typically do not have macropores and mesopores. However, materials without open pores may have micropores and nanopores. These micro- and nanopores are typically so small that they do not adversely affect materials where small pores are desirable.

Also, a polycrystalline material is a solid composed of a number of discrete microcrystals or grains with a grain boundary at the interface between any two microcrystals or grains in the material. Therefore, polycrystalline materials can have both intergranular/interstitial voids and intraparticle/interstitial voids. As used herein, the terms "voids between grains" and "voids between lattices" refer to voids between microcrystals or crystal grains (i.e., grain boundaries) of a polycrystalline material, and the terms "voids within particles" and "voids between grains" are used herein. By "pores in the body" is meant pores within individual crystallites or grains of a polycrystalline material. In contrast, a single crystal or single crystalline material is a solid with no grain boundaries and no intergranular/interstitial voids as the crystal lattice is continuous and uninterrupted throughout the entire volume of the material.

As used herein, the term "compact layer" refers to a layer having no mesopores or macropores. The compact layer may have micropores or nanopores depending on the case.

As used herein, the term “scaffold material” refers to a material that can act as a support for additional materials. Accordingly, the term "porous scaffold material" as used herein refers to a material that is itself porous and can act as a support for additional materials.

As used herein, the term "transparent" refers to a material or object that allows light to pass through with little obstruction so that objects behind it can be clearly seen. Thus, as used herein, the term “translucent” refers to a material having a transmittance (alternatively and equivalently referred to as transmittance) that transmits light intermediately between a transparent material or object and an opaque material or object, or means an object. Typically, transparent materials have an average transmittance for light of about 100%, or 90 to 100%. Typically, opaque materials have an average transmittance to light of about 0%, or 0 to 5%. Typically translucent materials or objects have an average transmittance to light of 10 to 90%, typically 40 to 60%. Unlike many translucent objects, translucent objects typically do not distort or blur images. The transmittance of light can be measured using a general method, for example, by comparing the intensity of incident light with the intensity of transmitted light.

As used herein, the term “electrode” refers to a conductive material or object that allows electrical current to enter or exit an object, substance or area. As used herein, the term “negative electrode” refers to an electrode through which electrons emitted from a material or object pass (ie, an electron collecting electrode). The negative electrode is typically referred to as the "anode". As used herein, the term “positive electrode” refers to an electrode through which holes emitted from a material or object pass (ie, a hole collecting electrode). The positive electrode is typically referred to as the "cathode". Within a photovoltaic device, electrons flow from the positive electrode/cathode to the negative electrode/anode, while holes flow from the negative electrode/anode to the positive electrode/cathode.

As used herein, the term "front electrode" means an electrode provided on one side or surface of a photovoltaic device that is intended to be exposed to sunlight. Therefore, the front electrode must be transparent or semi-transparent to allow light to pass through the electrode to the photoactive layer provided directly below the front electrode. Accordingly, the term "back electrode" as used herein means an electrode provided on one side or surface of the photovoltaic device opposite the side or surface intended to be exposed to sunlight.

The term "charge conductor" means a region, layer or material through which charge carriers (ie, charge-carrying particles) freely pass. In semiconductors, electrons act as mobile negative charge carriers and holes act as mobile positive charges. Accordingly, the term “electron conductor” refers to a region, layer or material through which electrons can readily flow and which can typically reflect holes (holes are electron-free which are considered mobile carriers of positive charge in semiconductors). it means. Conversely, the term "hole conductor" refers to a region, layer or material through which holes can readily flow, and which can typically reflect electrons.

The term "consisting essentially of" means a composition that includes essential components as well as other components, provided that the other components do not materially affect the essential properties of the composition. Typically, a composition consisting essentially of a particular component comprises at least 95 wt % or at least 99 wt % of that ingredient.

As used herein, the term “volatile compound” refers to a compound that is readily removed by evaporation or decomposition. For example, compounds that are readily removed by evaporation or decomposition at temperatures below 150°C, or for example below 100°C, will be volatile compounds. “Volatile compounds” also include compounds that are readily removed by evaporation through decomposition products. Thus, volatile compound X can readily evaporate through evaporation of molecules of X, or volatile compound X can readily evaporate by decomposition to form two readily evaporating compounds Y and Z. For example, an ammonium salt may be a volatile compound and may evaporate either as a molecule of the ammonium salt or as a decomposition product such as ammonium and a hydrogen compound (eg, a hydrogen halide). Thus, the volatile compound X has a relatively high vapor pressure (e.g., greater than 500 Pa) or relatively high decomposition pressure (e.g., greater than 500 Pa for one or more decomposition products), which may also be referred to as dissociation pressure. can

As used herein, the term "roughness" refers to the texture of a surface or edge and the degree to which it is uneven or irregular (and thus lacks smoothness or regularity). Roughness of a surface can be quantified by any measure of the deviation of the surface in a direction typically perpendicular to the mean surface. As a measure of roughness, the roughness average or average roughness (R _a ) is the arithmetic mean of the absolute values of all deviations from a straight line within a specified criterion or sampling length of a surface profile. An alternative measure of roughness, root mean square roughness (R _rms or R _q ) is the root mean square of the values of all deviations from a straight line within a specified criterion or sampling length of a surface profile.

As used herein, the term "bifacial" refers to a photovoltaic device/solar cell/sub-cell that generates electricity by collecting light through both the front, sun-exposed side and the back side. Bifacial devices/cells use direct sunlight as well as diffuse and reflected light to gain power. In contrast, the term "single-sided" refers to a photovoltaic device/solar cell/sub-cell that collects light only through its front, sun-exposed side to generate electricity.

As used herein, the term "conform" means an object having substantially the same shape or shape as another object. Accordingly, "conformal layer" as used herein refers to a layer of material that is conformal to the contours of the surface on which it is formed. In other words, the shape of the layer is such that the thickness of the layer is approximately constant across most of the interface between the layer and the surface on which it is formed.

device structure - general

1 schematically illustrates an integrally integrated multi-junction photovoltaic device 100 comprising a first/top sub-cell 110 comprising a photoactive region comprising a perovskite material, and a second /The lowermost sub-cell 120 includes a silicon heterojunction (SHJ). The present multi-junction type photovoltaic device 100 has an integrally integrated structure, and thus includes only two electrodes, a front/first electrode 101 and a rear/second electrode 102, these two electrodes The first/top sub-cell 110 and the second/bottom sub-cell 120 are disposed in between. In particular, the first sub-cell 110 contacts the first/front electrode 101 and the second sub-cell 120 contacts the second/back electrode 102 . The integrally integrated multi-junction photovoltaic device 100 also typically includes a metal grid on the top surface of the front/first electrode 101 as a top contact (not shown). As an example, the top contact may have a metal grid or fingers formed by screen printing of silver and/or copper paste.

Also, since the integrally integrated structure includes only two electrodes, the first sub-cell 110 and the second sub-cell 120 are interconnected by an intermediate region 130 comprising one or more interconnection layers. Connected. For example, the interconnect layer(s) may include either a recombination layer or a tunnel junction. In an integrally integrated multijunction type photovoltaic device, individual sub-cells are electrically connected in series, and as a result recombination layers or tunnel junctions and current matching are required between the sub-cells.

The perovskite material in the photoactive region 110 of the first sub-cell is configured to function as a light absorber (ie, photoresist) within the photoactive region. Therefore, as the uppermost sub-cell in the multi-junction type device, the perovskite material preferably has a band gap of 1.50 eV to 1.75 eV, more preferably 1.65 eV to 1.70 eV. The second sub-cell comprising a silicon heterojunction (SHJ) preferably has a band gap of about 1.1 eV.

In addition, the perovskite material in the photoactive region 110 of the first sub-cell may be configured to provide charge acceptance. In this regard, the perovskite material can act as a light absorber (ie photosensitizer) as well as an n-type, p-type or intrinsic (i-type) semiconductor material (charge conductor). Thus, perovskite materials can act as both photosensitizers and n-type semiconductor materials. Therefore, perovskite materials can play both roles of light absorption and long-range charge transport.

2 schematically illustrates one embodiment of a second/bottom sub-cell 120 comprising a silicon heterojunction (SHJ). In this regard, the term silicon heterojunction (SHJ) refers to a crystalline silicon (c-Si) wafer 121 as a photoactive absorber and amorphous silicon (a-Si) thin films 122, 123, 124, 125) means an amorphous silicon/crystalline silicon heterojunction. A silicon heterojunction (SHJ) is sometimes also referred to as a heterojunction with a thin intrinsic layer when any thin layer of intrinsic amorphous silicon (a-Si) is provided as a passivation/buffer layer. Thus, a silicon heterojunction (SHJ) typically consists of a p-type a-Si emitter (122), an intrinsic a-Si passivation/buffer layer (123), an n-type c-Si photoactive absorber (121), another intrinsic a-Si a passivation/buffer layer 124, and a back surface field (BSF) layer 125 made of n-type a-Si. Optionally, the silicon heterojunction (SHJ) may further include a layer of transparent conductive oxide (TCO) (eg, ITO) 126 between the back surface field (BSF) layer 125 and the back electrode 102. there is. A layer of TCO on this backside helps to maximize the infrared response by increasing the internal reflectance at the backside.

There are many advantages to using a silicon heterojunction (SHJ) as the second/bottom sub-cell 120 . First, monojunction solar cells based on silicon heterojunction (SHJ) technology have been found to achieve record energy conversion efficiencies exceeding 25%, which is achieved by using silicon heterojunction (SHJ) to achieve high efficiency. Maximize potential for multi-junction devices. Second, since the silicon heterojunction (SHJ) uses an n-type c-Si photoactive absorber 121 with a p-type a-Si emitter 122, a perovskite layer on the second sub-cell 120 as a substrate Formation of the first sub-cell 110 based on a single layer is initiated by the deposition of an n-type layer, then a perovskite material and a p-type layer are sequentially deposited, and the present inventors believe that this integrally integrated It has been found to be advantageous when processing perovskite-on-silicon multijunction photovoltaic devices.

3A-3F next schematically depict various embodiments of a first/top sub-cell 110 comprising a photoactive perovskite material.

3A and 3B, the first/top sub-cell 110 of the photovoltaic device 100 includes a porous region 114, wherein the porous region 114 comprises an n-type region 111 and a p-type region. and a layer (113) of perovskite material of formula (I) in contact with a porous scaffold material (115) disposed between (112). In this structure, the layer of perovskite material 113 is provided as a coating on the porous scaffold material 115, thereby forming a substantially conformal layer on the surface of the porous scaffold and thus the perovskite material 113 is disposed within the pores of the porous scaffold. The p-type region 112 contains a charge transport material that fills the pores of the porous region 114 (ie, the pores of the perovskite-coated porous scaffold) and forms a capping layer on the porous material. In this regard, the capping layer of charge transport material consists of a layer of charge transport material having no open pores.

In FIG. 3A , the illustrated photovoltaic device 100 has what is referred to as an ultrathin absorber (ETA) cell architecture, in which ultrathin layers of photoactive perovskite material are nanostructured interstitial n-type (e.g. , TiO2) and a p-type semiconductor (e.g., HTM). In this configuration, the porous scaffold material 115 in the first/top sub-cell 110 comprises a semiconductor/charge transport material.

In FIG. 3B , the first/top sub-cell 110 shown has what is referred to as a meso-superstructured solar cell (MSSC) architecture, in which an ultrathin layer of photoactive perovskite material is a mesoporous insulating scab. Provided on fold material. In this configuration, the porous scaffold material 115 in the first/top sub-cell 110 includes a dielectric material (eg, Al ₂ O ₃ ).

In FIG. 3C , the first/top sub-cell 110 includes a layer 113 of perovskite material of formula (I) with no open pores. As noted above, materials that do not have open pores typically do not have macropores and mesopores, but may have micropores and nanopores (and thus may have intercrystalline pores). Layer 113 of perovskite material thus forms a planar heterojunction with one or both of n-type region 111 and p-type region 112 . The n-type region 111 or the p-type region 112 may be disposed on a layer of perovskite material 113 that does not have open pores. In this regard, since the layer of perovskite material 113 does not have open pores, the n-type or p-type material does not penetrate the perovskite material and does not form a bulk heterojunction; Rather, it forms a planar heterojunction with the perovskite material. Typically, a layer of perovskite material 113 that does not have open pores is in contact with both the n-type and p-type regions, thus creating a planar heterojunction with both the n-type and p-type regions. form

Thus, the first/top sub-cell 110 shown in FIG. 3C has a thin-film planar heterojunction type device architecture, wherein the solid thin layer of photoactive perovskite material is n-type (eg, TiO ₂ ) and p-type semiconductor (e.g., HTM) plane layers. In this configuration, the device does not include porous scaffold material.

Next, FIGS. 3D, 3E, and 3F show an embodiment of a first/top sub-cell 110 similar to that shown in FIGS. Perovskite material 113 infiltrates into porous scaffold material 115 without forming a substantially conformal layer on the surface of fold material 115 . Thus, the perovskite material 113 fills the pores of the porous scaffold material 115 and together with the porous scaffold material 115 forms what may be considered a bulk heterojunction. In some embodiments, perovskite material 113 also forms capping layer 116 of perovskite material on porous scaffold material 115 . Capping layer 116 typically consists of a layer of perovskite material that does not have open pores, and in some embodiments forms a planar heterojunction with charge transport regions disposed on the perovskite material. form

In Fig. 3d, the perovskite material 113 completely penetrates into the nanostructured n-type (eg, TiO2), forming a planar heterojunction with the p-type semiconductor (eg, HTM). In this configuration, the porous scaffold material 115 in the first/top sub-cell 110 comprises a semiconductor/charge transport material.

The first/top sub-cell 110 shown in FIG. 3E is substantially the same as that shown in FIG. 3D , but it contains only one charge transport region. In this regard, it has been found that functional photovoltaic devices comprising photoactive perovskites can be formed without any hole-conducting materials, so that the photoactive perovskites can come into direct contact with electrodes and/or metal layers. (See Etgar, L., Gao, P. & Xue, Z., 2012. Mesoscopic CH ₃ NH ₃ PbI ₃ /TiO ₂ heterojunction solar cells. J. Am. Chem. Soc., 2012, 134 (42), pp 17396-17399). In these devices, the photoactive perovskite serves as both a light collector and a hole conductor so that no additional hole species material is needed. Thus, the first/top sub-cell 110 in FIG. 3E does not contain a p-type region, but the perovskite material 113 completely penetrates the nanostructured n-type material (e.g., TiO2). .

The first/top sub-cell 110 shown in FIG. 3F is similar to that of FIG. 3B , but the perovskite material 113 completely penetrates the mesoporous insulating scaffold material (Al ₂ O ₃ ) to form a p-type A planar heterojunction is formed with a semiconductor (e.g., HTM).

In an alternative structure, the photoactive region may include a layer of perovskite material of formula (I), wherein the perovskite material itself is porous. Therefore, the charge transport material fills the pores of the porous region of the perovskite material and forms a capping layer on the porous perovskite material. In this regard, the capping layer of charge transport material consists of a layer of charge transport material having no open pores.

FIG. 4 schematically illustrates one embodiment of an integrally integrated multi-junction photovoltaic device 100, wherein the first/top sub-cell 110 has a photoactive perovskite material 113 formed on a planar surface. and a photoactive region provided as a layer. In the embodiment of Figure 4, the photoactive region 110 of the first sub-cell comprises an n-type region 111 comprising one or more n-type layers, a p-type region 112 comprising one or more p-type layers, and and a layer 113 of planar perovskite material disposed between the n-type region and the p-type region. The first sub-cell 110 and the second sub-cell 120 are connected to each other by a middle region 130 including an interconnection layer.

In this configuration, the layer 113 of planar perovskite material is considered free of open pores 113 . As noted above, materials that do not have open pores typically do not have macropores and mesopores, but may have micropores and nanopores (and thus may have intercrystalline pores). In this regard, since the layer of perovskite material 113 does not have open pores, the n-type or p-type material does not penetrate the perovskite material and does not form a bulk heterojunction; Rather, it forms a planar heterojunction with the perovskite material. Typically, a layer of perovskite material 113 that does not have open pores is in contact with both the n-type and p-type regions, thus creating a planar heterojunction with both the n-type and p-type regions. form Thus, the first sub-cell 110 can be described as having a planar heterojunction architecture (similar to that of the aforementioned first sub-cell 110 shown in FIG. 3C).

As described above, the second/bottom sub-cell 120 comprises a silicon heterojunction (SHJ), wherein the photoactive absorber is n-type c-Si (121) and the emitter is p-type a-Si (122) Assuming that , the first/top sub-cell 110 of the multi-junction photovoltaic device 100 is disposed so that the n-type region 111 is adjacent to the second sub-cell 120 . In other words, the n-type region 111 is adjacent to the second sub-cell 120 and thus closer to the second sub-cell 120 than the p-type region 112 is. In particular, it is the n-type region 111 of the first sub-cell 110 that is in contact with the middle region 130 connecting the first sub-cell 110 to the second sub-cell 120 . Thus, the p-type region 112 of the first sub-cell 110 is in contact with the first electrode 101 . Thus, the front/first electrode 101 functions as a positive electrode (hole collecting electrode), while the second/back electrode 102 functions as a negative electrode (electron collecting electrode).

In the aforementioned multi-junction photovoltaic device, the p-type region of the first sub-cell includes one or more p-type layers. Usually, the p-type region is a p-type layer, i.e., a single p-type layer. However, in other embodiments, the p-type region may include a p-type layer and a p-type exciton blocking layer or electron blocking layer. If the valence band of the exciton blocking layer (or the highest occupied molecular orbital energy level) is closely aligned with the valence band of the photoactive material, holes can pass through the exciton blocking layer from the photoactive material, or through the exciton blocking layer to become photoactive. It can penetrate into the material and is called the p-type exciton blocking layer. An example of this is tris[4-(5-phenylthiophen-2-yl)phenyl]amine [Masaya Hirade, and Chihaya Adachi, "Small molecular organic photovoltaic cells with exciton blocking layer at anode interface for improved device performance" Appl. Phys. Lett. 99, 153302 (2011)].

The p-type layer is a layer of hole transporting (ie, p-type) material. The p-type material can be a single p-type compound or elemental material, or a mixture of two or more p-type compounds or elemental materials, which can be undoped or doped with one or more dopant elements.

The p-type layer may include inorganic or organic p-type materials. Typically, the p-type region includes a layer of organic p-type material.

Suitable p-type materials may be selected from polymers or molecular hole conductors. The p-type layer employed in the photovoltaic device of the present invention is, for example, spiro-OMeTAD(2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9 ,9'-spirobifluorene)), P3HT (poly(3-hexylthiophene)), PCPDTBT (poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis( 2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl]]), PVK (poly(N-vinylcarbazole)), HTM- TFSI (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide), Li-TFSI (lithium bis(trifluoromethanesulfonyl)imide) or tBP (tert-butylpyridine) can include The p-type region may include carbon nanotubes. Typically, the p-type material is selected from Spiro-OMeTAD, P3HT, PCPDTBT and PVK. Preferably, the p-type region consists of a p-type layer comprising spiro-MeOTAD.

The p-type layer is, for example, spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) ), P3HT (poly (3-hexylthiophene)), PCPDTBT (poly [2,1,3-benzothiadiazole-4,7-diyl [4,4-bis (2-ethylhexyl) -4H-cyclo penta[2,1-b:3,4-b']dithiophene-2,6-diyl]]), or PVK (poly(N-vinylcarbazole)).

Suitable p-type materials also include molecular hole transporters, polymeric hole transporters and copolymer hole transporters. The p-type material can be, for example, a molecular hole transport material, polymer or copolymer comprising one or more of the following components: thiophenyl, phenerenyl, dithiazolyl, benzothiazolyl, diketopyrrolopyrroyl , ethoxydithiophenyl, amino, triphenyl amino, carbozolyl, ethylene dioxythiophenyl, dioxythiophenyl, or fluorenyl. Thus, the p-type layer employed in the photovoltaic device of the present invention may include, for example, any one of the aforementioned molecular hole transport materials, polymers or copolymers.

Suitable p-type materials are also m-MTDATA(4,4',4''-tris(methylphenylphenylamino)triphenylamine), MeOTPD( N , N , N ' , N' -tetrakis(4-methoxyphenyl) )-benzidine), BP2T (5,5'-di(biphenyl-4-yl)-2,2'-bithiophene), Di-NPB(N,N'-di-[(1-naphthyl)- N,N' -diphenyl]-1,1'-biphenyl)-4,4'-diamine), α-NPB (N,N'-di(naphthalen-1-yl)-N,N'-di phenyl-benzidine), TNATA (4,4',4"-tris-(N-(naphthylene-2-yl)-N-phenylamine)triphenylamine), BPAPF (9,9-bis[4-( N,N-bis-biphenyl-4-yl-amino)phenyl]-9H-fluorene), spiro-NPB(N2,N7-di-1-naphthalenyl-N2,N7-diphenyl-9,9 '-spirobi[9H-fluorene]-2,7-diamine), 4P-TPD(4,4-bis-( N , N -diphenylamino)-tetraphenyl), PEDOT:PSS and spiro-OMeTAD.

The p-type layer can be doped using, for example, tertbutyl pyridine and LiTFSI. The p-type layer can be doped to increase the hole density. The p-type layer can be doped with, for example, NOBF ₄ (nitrosonium tetrafluoroborate) to increase the hole density.

In another embodiment, the p-type layer can include an inorganic hole transporter. For example, the p-type layer may be an oxide of nickel, vanadium, copper or molybdenum; CuI, CuBr, CuSCN, Cu ₂ O, CuO or CIS; perovskite; amorphous Si; p-type group IV-semiconductor, p-type group III-VI semiconductor, p-type group II-VI semiconductor, p-type group I-VII semiconductor, p-type group IV-VI semiconductor, p-type group V-VI semiconductor, and p-type II An inorganic hole transporter comprising a group-V semiconductor, which inorganic material may be doped or undoped. The p-type layer may be a compact layer of the inorganic hole transporter.

The p-type layer may be, for example, an oxide of nickel, vanadium, copper or molybdenum; CuI, CuBr, CuSCN, Cu ₂ O, CuO or CIS; amorphous Si; p-type group IV-semiconductor, p-type group III-VI semiconductor, p-type group II-VI semiconductor, p-type group I-VII semiconductor, p-type group IV-VI semiconductor, p-type group V-VI semiconductor, and p-type II An inorganic hole transporter comprising a group-V semiconductor, which inorganic material may be doped or undoped. The p-type layer may include, for example, an inorganic hole transporter selected from CuI, CuBr, CuSCN, Cu ₂ O, CuO and CIS. The p-type layer may be a compact layer of the inorganic hole transporter.

The p-type region may have a thickness of 50 nm to 1000 nm. For example, the p-type region may have a thickness of 50 nm to 500 nm, or 100 nm to 500 nm. In the aforementioned multi-junction photovoltaic device, the p-type region 112 of the first sub-cell preferably has a thickness of 200 nm to 300 nm, more preferably about 250 nm.

In the aforementioned multi-junction photovoltaic device, the n-type region of the first sub-cell includes one or more n-type layers. Usually, the n-type region is an n-type layer, i.e., a single n-type layer. However, in other embodiments, the n-type region may include an n-type layer and a separate n-type exciton blocking layer or hole blocking layer.

An exciton blocking layer is a material that has a wider band gap than the photoactive material, but whose conductivity band or valence band closely matches that of the photoactive material. When the conduction band of the exciton blocking layer (or the lowest unoccupied molecular orbital energy level) is closely aligned with the conduction band of the photoactive material, electrons pass through the exciton blocking layer from the photoactive material or enter the photoactive material through the exciton blocking layer. This is called the n-type exciton blocking layer. An example of this is bathocuproine (BCP) [P. Peumans, A. Yakimov, and S. R. Forrest, "Small molecular weight organic thin-film photodetectors and solar cells" J. Appl. Phys. 93, 3693 (2001) and Masaya Hirade, and Chihaya Adachi, "Small molecular organic photovoltaic cells with exciton blocking layer at anode interface for improved device performance" Appl. Phys. Lett. 99, 153302 (2011)].

The n-type layer is a layer of electron transport (ie n-type) material. The n-type material can be a single n-type compound or elemental material, or a mixture of two or more n-type compounds or elemental materials, which can be undoped or doped with one or more dopant elements.

The n-type layer employed may include inorganic or organic n-type materials.

Suitable inorganic n-type materials include metal oxides, metal sulfides, metal selenides, metal tellurides, perovskites, amorphous Si, n-type group IV semiconductors, n-type III-V group semiconductors, n-type II-VI group semiconductors, n-type I-VII group semiconductor, n-type IV-VI group semiconductor, n-type V-VI group semiconductor, and n-type II-V group semiconductor, any one of which may be doped or undoped. .

N-type materials include metal oxides, metal sulfides, metal selenides, metal tellurides, amorphous Si, n-type group IV semiconductors, n-type III-VI semiconductors, n-type II-VI group semiconductors, and n-type I-VII group semiconductors. , an n-type IV-VI group semiconductor, an n-type V-VI group semiconductor, and an n-type II-V group semiconductor, any one of which may be doped or undoped.

More typically, the n-type material is selected from metal oxides, metal sulfides, metal selenides, and metal tellurides.

Accordingly, the n-type layer may comprise an inorganic material selected from oxides of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, or cadmium, or oxides of mixtures of two or more of the foregoing metals. can For example, the n-type layer is TiO ₂ ,SnO ₂ ,ZnO,Nb ₂ O ₅ ,Ta ₂ O ₅ ,WO ₃ ,W ₂ O ₅ ,In ₂ O ₃ ,Ga ₂ O ₃ ,Nd ₂ O ₃ ,PbO , or CdO.

Other suitable n-type materials that may be used include sulfides of cadmium, tin, copper, or zinc and sulphides of mixtures of two or more of these metals. For example, the sulfide may be FeS ₂ , CdS, ZnS, SnS, bis, SbS, or Cu ₂ ZnSnS ₄ .

For example, the n-type layer may be a selenide of cadmium, zinc, indium, or gallium; a selenide of a mixture of two or more of the above metals; or a telluride of cadmium, zinc, cadmium or tin, or a telluride of a mixture of two or more of the above metals. For example, the selenide may be Cu(In,Ga)Se ₂ . Typically, the telluride is a telluride of cadmium, zinc, cadmium or tin. For example, telluride may be CdTe.

The n-type layer may be, for example, an oxide of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or an oxide of a mixture of two or more of the foregoing metals; sulfides of cadmium, tin, copper, zinc or sulfides of mixtures of two or more of the foregoing metals; selenides of cadmium, zinc, indium, gallium, and selenides of mixtures of two or more of the above metals; or an inorganic material selected from tellurides of cadmium, zinc, cadmium or tin, or tellurides of a mixture of two or more of the above metals.

Examples of other semiconductors that may be suitable n-type materials include, for example, group IV element or compound semiconductors when they are n-doped; amorphous Si; III-V semiconductors (eg gallium arsenide); Group II-VI semiconductors (eg, cadmium selenide); Group I-VII semiconductors (eg cuprous chloride); Group IV-VI semiconductors (eg, lead selenide); Group V-VI semiconductors (eg, bismuth telluride); and II-V group semiconductors (eg, cadmium arsenide).

Typically, the n-type layer includes TiO ₂ .

If the n-type layer is an inorganic material, such as TiO ₂ , or any of the other materials described above, it may be a compact layer of said inorganic material. Preferably, the n-type layer is a compact layer of TiO ₂ .

Other n-type materials may also be used, including organic and polymeric electron transport materials, and electrolytes. Suitable examples are fullerene or a fullerene derivative, an organic electron transport material comprising perylene or a derivative thereof, or poly{[N,N0-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis (dicarboximide)-2,6-diyl]-alt-5,50-(2,20-bithiophene)} (P(NDI2OD-T2)). For example, the n-type region may include an n-type layer comprising one or more of C60, C70, C84, C60-PCBM, C70-PCBM, C84-PCBM, and carbon nanotubes.

The n-type region may have a thickness of 5 nm to 1000 nm. When the n-type region includes a compact layer of an n-type semiconductor, this compact layer has a thickness of 5 nm to 200 nm. In the multi-junction photovoltaic device described above, the n-type region 111 of the first sub-cell 110 is preferably 10 nm to 1000 nm thick, more preferably 20 nm to 40 nm thick, More preferably, it has a thickness of about 30 nm.

In the aforementioned multi-junction photovoltaic device, the intermediate region 130 may include one or more interconnection layers. As an example, the interconnect layer may include a transparent conducting oxide (TCO) such as indium tin oxide (ITO) or aluminum doped zinc oxide (AZO), carbon (eg, graphene), metal nanowires, and the like. Typically, the intermediate region includes an interconnect layer made of indium tin oxide (ITO) that acts as a recombination layer. The interconnect layer of ITO preferably has a thickness of 10 nm to 60 nm, more preferably about 50 nm.

The back electrode 102 typically comprises a high work function metal such as gold (Au) silver (Ag), nickel (Ni), palladium (Pd), platinum (Pt) or aluminum (Al).

device Structure - transparent electrode

In the multi-junction type photovoltaic device described above, the first/front electrode 101 is an electrode provided on a side surface or surface of the photovoltaic device to be directly exposed to sunlight. Therefore, the first electrode 101 must be transparent to maximize the transmittance of light through this electrode to the photoactive layers of the first sub-cell 110 and the second sub-cell 120 provided on the lower side, and also must be sufficiently electrical. It must have conductivity. In particular, for multi-junction devices, the first electrode transmits a large percentage of light over the complete optical window (i.e., wavelengths from 400 nm to 1200 nm) since transmission of longer wavelengths is critical to achieving useful power conversion efficiency. should be permeated

Therefore, the first electrode 101 has a sheet resistance (Rs) of 10 ohm/square (Ω/sq) to 100 Ω/sq and an average transmittance for visible light and infrared rays of 85% or more (ie, wavelengths of 400 nm to 1200 nm). It is preferably made of a material that transmits at least 85% of light). More preferably, the first electrode 101 has a sheet resistance (Rs) of 50 Ω/sq or less and an average transmittance of more than 90% for visible and infrared light, preferably an average transmittance of 95% or more for visible and infrared light. made of a material with

Materials particularly suitable for use as the transparent front electrode include transparent conducting oxides (TCOs). Transparent conductive oxides (TCOs) are doped metal oxides that are electrically conductive and have relatively low light absorption. The TCO may have transmittance in excess of 80% for incident light as well as conductivity in excess of 10 ⁴ S/cm (ie, resistivity of ˜10 ^{−4 Ω} ·cm) for efficient carrier transport. Examples of suitable TCO materials are indium tin oxide (ITO), aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), indium-doped zinc oxide (IZO), niobium-doped titanium dioxide (Nb :TiO ₂ ) and the like.

Therefore, the first electrode 101 is preferably composed of a layer of transparent conductive oxide (TCO). By way of example, the first electrode 101 may be indium tin oxide (ITO), aluminum doped zinc oxide (AZO), fluorine doped tin oxide (FTO), indium-doped zinc oxide (IZO), and niobium-doped It may be composed of any one layer of titanium dioxide (Nb:TiO ₂ ). Therefore, more preferably, the first electrode 101 is preferably made of a layer of indium tin oxide (ITO). When the first electrode 101 is made of a layer of indium tin oxide (ITO), this layer preferably has a thickness of 100 nm to 200 nm, more preferably 150 nm.

Conventional techniques for fabricating layers of TCO materials typically include magnetron sputtering processes. However, a number of drawbacks exist when using conventional magnetron sputtering to deposit layers of TCO material. In particular, while conventional magnetron sputtering traps free electrons in a magnetic field directly above the target surface, the plasma generated is still relatively diffuse and must therefore be of high energy to produce a layer of sufficient quality. When high-energy plasma is used in a conventional magnetron sputtering process, high-energy target atoms collide on the surface of a substrate, which may cause damage when the surface of the substrate is sensitive, such as when the substrate includes an organic material. While it is possible to reduce the power and thereby lower the energy of the plasma used in the process, this will degrade the quality of the layer deposited by conventional magnetron sputtering, and disorder/disorder with defects that can act as traps. Creating an irregular structure reduces carrier mobility, increases resistivity, and reduces transmittance.

Consequently, in order to be able to use an organic charge transport material in the p-type region of the first sub-cell 110 without requiring an additional protective inorganic buffer layer, the present inventors have employed TCO as the first electrode 101. A sputtering process involving a remotely generated plasma was used to deposit a layer of . The term "remotely generated plasma" means a plasma whose production does not depend on the sputtering target (as in conventional magnetron sputtering). The remotely generated plasma is guided to the sputtering target by a shaped electromagnetic field generated by a pair of electromagnets, forming a uniformly high-density (eg, 10 ¹¹ cm ^{-3 or} more) plasma over the entire surface area of the target. do.

The use of remotely generated plasma for the sputtering deposition process blocks the generation of plasma from biasing of the target, making it possible to generate a high-density (5 x 10 ¹³ cm ^{- 3} ) low-energy plasma. It happens. In this regard, using remote plasma sputtering, the energy of the ions in the plasma is typically in the range of 30 to 50 eV, which is insufficient to sputter from a target in conventional magnetron sputtering processes. With remote plasma sputtering, it is possible to control the energy of the sputtering regardless of the energy of the plasma by controlling the biasing applied to the target.

The inventors found that this low-energy sputtering process not only prevents damage to the substrate but also produces a layer of TCO with good short-range order and sufficiently few defects, compared to a layer produced using conventional magnetron sputtering. It was found that it improves the mobility of and the optical transmittance of the resulting layer. This is particularly important in the case of multijunction type photovoltaic devices where it is important that as much light as possible reach multiple photoactive layers within the device.

In particular, in the case of the layer of TCO, the improvement in the quality of the resulting layer improves the carrier mobility while at the same time for improved transmittance in excess of 90% for visible and infrared light (i.e., light with a wavelength exceeding 400 nm). Limit the carrier concentration (e.g. ~1x10 ²¹ cm ^{- 3} ) and still have a low resistivity (e.g. ~7x10 ^{- 4} Ω equivalent to a sheet resistance of ~50 Ω/sq for a 150 nm thick layer). .cm) is provided. Using conventional techniques, layers of TCO that achieve these properties require high sputtering target power densities (and thus high damage) or high temperature annealing during their fabrication, making them incompatible with substrates composed of high temperature sensitive materials. .

In addition, when remotely generated plasma is used for the sputtering deposition process, the structure of the TCO layer generated by changing/adjusting any one of plasma power, biasing applied to the target, and sputtering gas pressure can be finely tuned. can be regulated. Changing the plasma power changes the ion density of the plasma, while changing the target biasing can affect the sputtering energy, while changing the pressure can affect the reactivity and kinetic energy of the species reaching the substrate. can As an example, this control can produce a layer of high-density, homogeneous amorphous TCO with good short-range order and low defects, which is suitable for use as a barrier layer to protect the underlying layer. In particular, penetration of moisture through the layer of TCO is prevented due to the absence of defects and grain boundaries. Similarly, this control can produce a layer of TCO that gradually changes between an amorphous structure and a crystalline structure. The amorphous portion then provides a barrier layer and the crystalline portion provides improved electrical conductivity. Moreover, this control can be used to relieve stress in the TCO layer during deposition, resulting in a layer that is more robust, less prone to cracking, and has improved adhesion.

While the foregoing embodiments relate to a layer of TCO for use as the front electrode of a multijunction photovoltaic device, a layer of TCO having advantageous properties produced using a remotely generated plasma for a sputter deposition process is only Equally applicable to other optoelectronic devices including bonded photovoltaic devices, light emitting devices, and the like. Moreover, while the foregoing embodiment relates to the use of a layer of TCO deposited on the p-type region of a perovskite-based solar cell, it may equally apply to an inverted structure in which a layer of TCO is deposited on an n-type material. can

Consequently, there is also provided a photovoltaic device comprising a photoactive layer, a layer of organic charge transport material on the photoactive layer, and a layer of TCO deposited on the layer of organic charge transport material, wherein the layer of TCO is 50 Ohm/ Sheet resistance (Rs) of less than square (Ω/sq) and average transmittance greater than 90% for visible and infrared light (i.e., transmits at least 90% of light with a wavelength greater than 400 nm), preferably visible and infrared light It has an average transmittance of 95% or more for infrared rays. The photovoltaic device also includes depositing a photoactive layer, depositing a layer of organic charge transport material on the photoactive layer, and depositing a layer of TCO on the organic charge transport material using remote plasma sputtering. A method for producing is provided. Advantageously, the step of depositing the layer of TCO in the method can be carried out at a temperature of less than 100°C. In addition, the method does not require an additional step of annealing the deposited layer of TCO at a temperature above 200°C. In a preferred embodiment, the photoactive layer comprises a photoactive perovskite material.

device structure - perovskite ingredient

In the aforementioned multi-junction photovoltaic device, the first sub-cell 110 includes a photoactive region including a perovskite material. The perovskite material in the photoactive region 110 of the first sub-cell is configured to function as a light absorber/sensitizer within the photoactive region. Then, the perovskite material preferably has a band gap of 1.50 eV to 1.75 eV, more preferably 1.65 eV to 1.70 eV. The second sub-cell comprising a silicon heterojunction (SHJ) preferably has a band gap of about 1.1 eV.

Preferably, the perovskite material has the general formula (I).

[A][B][X] ₃ (I)

wherein [A] is one or more monovalent cations, [B] is one or more divalent inorganic cations, and [X] is one or more halide anions.

Preferably [X] comprises at least one halide anion selected from fluoride, chloride, bromide, and iodide, preferably selected from chloride, bromide and iodide. More preferably [X] contains at least one halide anion selected from bromide and iodide. In some embodiments, [X] preferably comprises two different halide anions selected from fluoride, chloride, bromide, and iodide, preferably selected from chloride, bromide, and iodide; , more preferably bromide and iodide.

Preferably [A] is one or more organic cations selected from methylammonium (CH ₃ NH ₃ ⁺ ), formamidinium (HC(NH) ₂ ) ₂ ⁺ ), and ethyl ammonium (CH ₃ CH ₂ NH ₃ ⁺ ). and preferably one organic cation selected from methylammonium (CH ₃ NH ₃ ⁺ ) and formamidinium (HC(NH) ₂ ) ₂ ⁺ . [A] may include one or more inorganic cations selected from Cs+, Rb+, Cu+, Pd+, Pt+, Ag+, Au+, Rh+, and Ru+.

Preferably [B] contains ^at least one divalent inorganic cation selected from Pb ²⁺ and Sn ²⁺ , preferably ^{Pb 2+} .

In a preferred embodiment, the perovskite material has the general formula (Ia).

A _x A' _1-x B(X _y X' _1-y ) ₃ (IA)

where A is formamidinium (FA), A ^' is a cesium cation (Cs ⁺ ), B is Pb ²⁺ , X is an iodide, X' is a bromide, and 0 < x ≤ 1 , 0 < y ≤ 1. Thus, in these preferred embodiments, the perovskite material may include a mixture of two monovalent cations. Also, in a preferred embodiment, the perovskite material may thus comprise a single iodide anion or a mixture of iodide and bromide anions. The inventors have discovered that these perovskite materials can have band gaps of 1.50 eV to 1.75 eV and that layers of these perovskite materials can be readily formed into suitable crystal morphologies and phases. More preferably, the perovskite material is FA _{1- x} Cs _x PbI _{3 - y} B _y .

In order to provide a photovoltaic device with high efficiency, it is ideal that the absorption of the absorber is maximized to produce an optimal amount of amperage. Consequently, when using perovskite as an absorber within a photovoltaic device or sub-cell, the thickness of the perovskite layer ideally is about 300 to 600 nm in order to absorb most of the sunlight across the visible spectrum. should be Thus, typically the thickness of the layer of perovskite material exceeds 100 nm. The thickness of the layer of perovskite material of the photovoltaic device can be, for example, between 100 nm and 1000 nm. The thickness of the layer of perovskite material of the photovoltaic device is, for example, between 200 nm and 700 nm, preferably between 300 nm and 600 nm. In the aforementioned multi-junction photovoltaic device, the layer 113 of planar perovskite material in the photoactive region of the first/top sub-cell 110 preferably has a thickness of 350 nm to 450 nm, more preferably preferably has a thickness of about 400 nm.

device structure - No. 2 Sub-cell surface profile

In the development of monolithically integrated perovskite-on-silicon multijunction photovoltaic devices, one of the most important considerations is the interface between the perovskite sub-cell and the adjacent crystalline silicon lowermost sub-cell. . In this regard, the aforementioned Schneider, B.W. As described in et al. and Filipic, M., conventional commercial crystalline silicon solar cells feature a textured surface, which is designed to reduce reflection and increase the length of the optical path, typically This surface texture consists of irregularly distributed pyramids formed by etching along the crystal plane, or regular inverted pyramids. Thus, since the overall thickness of the perovskite sub-cell typically approximates the roughness of the textured surface, such a textured surface presents significant challenges for the fabrication of integrally integrated perovskite-on-silicon photovoltaic devices. there is. For example, the surface roughness of conventional crystalline silicon solar cells typically ranges from 500 nm to 10 μm, and the thickness of perovskite cells is typically less than 1 μm. In particular, Schneider, B.W. et al. and Filipic, M. et al. attempted to model a perovskite-on-silicon tandem cell in which a conformal thin-film perovskite sub-cell was deposited on a textured front surface of a silicon bottom sub-cell, but no literature Nor does it suggest a method for achieving such conformal deposition. Furthermore, Bailie, C. et al. found that the development of an integral tandem cell incorporating a perovskite top cell requires planarization of the surface silicon bottom cell (i.e., to reduce surface roughness/remove any surface texture). say there will be

As a result, to date, the only realization of monolithically integrated perovskite-on-silicon multijunction photovoltaic devices is the deposition of perovskite, despite the recognition that it reduces the efficiency of the silicon bottom sub-cell. For simplicity, a silicon bottom sub-cell with a planar top surface is used (see Mailoa, J.P. et al., supra). This approach avoids the problems associated with the deposition of perovskite cells, but requires mechanical polishing of conventional crystalline silicon solar cells to create a planar surface, thus increasing the processing cost of the silicon cells and reducing their efficiency. let it

In contrast, we maintain most of the efficiency benefits arising from the presence of texturing of the uppermost surface of the silicon lowermost sub-cell while enabling the deposition of a layer comprising a perovskite uppermost sub-cell having a suitable morphology. It has been found that it is possible to fabricate an integrally integrated perovskite-on-silicon multijunction photovoltaic device. In particular, we found that while enabling simple conformal deposition of the layers of the perovskite top sub-cell, about 1% of the silicon bottom sub-cell compared to a silicon bottom sub-cell with a planar, untextured top surface. We have found an advantageous surface profile for the top surface of the silicon bottom sub-cell that allows for an increase in the efficiency of the cell.

In this regard, the present inventors have found that when depositing a perovskite sub-cell on a silicon bottom sub-cell where the surface adjacent to the perovskite sub-cell is textured with a roughness average (R _a ) of less than 500 nm, functional It was decided that a tandem could be obtained. As noted above, the term “textured” in relation to silicon-based photovoltaic devices refers to the surface of the device where an intentionally created, artificially uneven surface profile has been created using, for example, an etching process.

The inventors have also determined that a roughness average (R _a ) of 50 to 450 nm is desirable, which allows the layer of the perovskite sub-cell to be reconstructed without completely losing the advantage provided by the surface texturing of the silicon bottom sub-cell. Because it simplifies calm. In particular, depending on the particular perovskite used and the thickness of the perovskite layer to be deposited on the silicon bottom cell, roughness averages (R _a ) of 100 to 400 nm are likely to produce the most efficient devices. In the exemplary embodiments described herein, the preferred roughness average (R _a ) for the surface of the lowermost silicon sub-cell adjacent to the perovskite sub-cell is between 200 nm and 400 nm.

Accordingly, the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 preferably has a roughness average R _a of less than 500 nm. It is even more preferable that the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 has a roughness average R _a of 50 to 450 nm. In a preferred embodiment, the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 has a roughness average R _a of 100 to 400 nm, more preferably 200 nm to 400 nm of roughness average (R _a ).

In a preferred embodiment, the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 has a root mean square roughness (R _rms ) of 50 nm or less. Also then, the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 has a peak-to-peak roughness (R _t ) of 100 nm to 400 nm, preferably about 250 nm. It is desirable to have Moreover, the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 has an average peak-to-peak spacing S _m of between 10 μm and 50 μm, preferably about 25 μm. it is desirable Moreover, the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 preferably has an undulating profile (ie, the profile is such that the change in height of the surface is substantially smooth). have the shape or contour of a wave). The layers above the second sub-cell 120 (eg, the interconnect layer 130 and the layers constituting the first sub-cell 110) then form an adjacent surface 120 of the second sub-cell. are each deposited as a substantially continuous, conformal layer that is conformal with

As an example, FIG. 5 schematically (not to scale) shows a characteristic embodiment of the surface profile of the second sub-cell 120 , where the textured surface is 500 (ie for a sampling length L) nm, a peak-to-peak roughness (R _t ) of about 250 nm, a root mean square _roughness (R _rms ) of about 50 nm, and an average spacing between peaks (S _m ) of It is about 25 μm. It can also be seen that the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110 has an undulating profile such that the change in height of the surface is substantially smooth.

alternative device structure - general

In the foregoing embodiments, the multi-junction type photovoltaic device may be regarded as a single-sided type configured to generate electricity by collecting light only through the sun-exposed surface of its front surface. However, most of the features described above are equally applicable to a double-sided, multi-junction type photovoltaic device capable of generating electricity by collecting light through both sides thereof, ie, the front sun-exposed side and the back side. In particular, the inventors found that the multijunction photovoltaic device can be constructed in a bifacial architecture with an additional perovskite-based sub-cell provided on the underside of the second sub-cell for light absorbed from the rear surface of the device. recognized.

Figure 6 thus schematically depicts a bifacial, integrally integrated, multi-junction photovoltaic device 100, which comprises a first/top sub-cell 110 comprising a photoactive region comprising a perovskite material. , a second/middle sub-cell 120 comprising a silicon heterojunction (SHJ), and a third/bottom sub-cell 140 comprising a photoactive region comprising a perovskite material. The multi-junction type photovoltaic device 100 has an integrally integrated structure, and thus has only two electrodes, namely a front/first electrode 101 and a rear/second electrode 102, between these two electrodes. The first sub-cell 110, the second sub-cell 120, and the third sub-cell 140 are disposed in. Specifically, the first sub-cell 110 is in contact with the first electrode 101, the third sub-cell 140 is in contact with the second/rear electrode 102, and the second sub-cell 120 is disposed between the first sub-cell 110 and the third sub-cell 140 .

Since the integrally integrated structure has only two electrodes, the first sub-cell 110 and the second sub-cell 120 are interconnected by a first intermediate region 130 comprising one or more interconnection layers. and the second sub-cell 120 and the third sub-cell 140 are connected to each other by a second intermediate region 150 comprising one or more interconnection layers.

As with the device described above, the perovskite material within the photoactive region 110 of the first sub-cell is configured to function as a light absorber/sensitizer within the photoactive region. Then, the perovskite material preferably has a band gap of 1.50 eV to 1.75 eV, more preferably 1.65 eV to 1.70 eV. The second sub-cell comprising a silicon heterojunction (SHJ) preferably has a band gap of about 1.1 eV. The perovskite material in the photoactive region 140 of the third sub-cell is also configured to function as a light absorber/photosensitizer in the photoactive region, and thus preferably has a band gap of 1.50 eV to 1.75 eV, more preferably 1.65 eV. It has a band gap from eV to 1.70 eV.

Thus, the perovskite material in the photoactive region 140 of the third sub-cell is the same as the perovskite material in the photoactive region 110 of the first sub-cell or the photoactive region 110 of the first sub-cell. It may be different from the perovskite material in In any case, the perovskite material in the photoactive region 140 of the third sub-cell preferably corresponds to the preferred perovskite material described herein.

7 schematically illustrates a more specific embodiment of a double-sided integrally integrated multi-junction photovoltaic device 100 . In the embodiment of FIG. 7 , the structure photoactive region of the first sub-cell 110 corresponds to that shown in FIG. 3 and described with reference thereto. The photoactive region 140 of the third sub-cell thus comprises a photoactive region in which the photoactive perovskite material is provided as a planar layer 143 . The photoactive region 140 of the third sub-cell includes an n-type region 142 comprising one or more n-type layers, a p-type region 141 comprising one or more p-type layers, and an n-type region and a p-type region. and a layer 143 of planar perovskite material disposed therebetween.

In this configuration, the layer 143 of planar perovskite material in the third sub-cell 140 is considered free of open pores. Typically, the layer 143 of perovskite material without open pores is in contact with both the n-type and p-type regions, thus forming a planar heterojunction with both the n-type and p-type regions. do. Thus, the third sub-cell 140 can be described as having a planar heterojunction architecture.

As described above, the second/middle sub-cell 120 comprises a silicon heterojunction (SHJ), wherein the photoactive absorber is n-type c-Si (121) and the emitter is p-type a-Si (122) , the first/top sub-cell 110 of the multi-junction photovoltaic device 100 is disposed such that the n-type region 111 is adjacent to the second sub-cell 120 . In other words, the n-type region 111 is adjacent to the second sub-cell 120 and thus closer to the second sub-cell 120 than the p-type region 112 is. In particular, it is the n-type region 111 of the first sub-cell 110 that contacts the first middle region 130 connecting the first sub-cell 110 and the second sub-cell 120 . Thus, the p-type region 112 of the first sub-cell 110 is in contact with the first electrode 101 . Thus, the front/first electrode 101 functions as a positive electrode (hole collecting electrode).

Similarly, the second/middle sub-cell 120 includes a silicon heterojunction (SHJ), wherein the photoactive absorber is n-type c-Si (121) and the back surface field (BSF) layer is n-type a-Si (125), the third/bottom sub-cell of the multi-junction photovoltaic device 100 is disposed such that the p-type region 141 is adjacent to the second sub-cell 120. In other words, the p-type region 141 is adjacent to the second sub-cell 120 and thus closer to the second sub-cell 120 than the n-type region 142 is. In particular, the p-type region 141 of the third sub-cell 140 contacts the second middle region 150 connecting the third sub-cell 140 and the second sub-cell 120 . Thus, the third sub-cell 140 can be considered reversed when compared to the first sub-cell 110 since the order of the layers deposited on the second sub-cell 120 was reversed during fabrication. there is. Thus, the n-type region 142 of the third sub-cell 140 is in contact with the second electrode 102, and thus the second/rear electrode 102 functions as a negative electrode (electron collecting electrode).

In the double-sided multi-junction photovoltaic device, each of the p-type region 141 and the n-type region 142 corresponds to each of the p-type region 112 and the n-type region 111 of the first sub-cell 110. may be of the same composition and structure. Alternatively, the p-type region 141 and the n-type region 142 may have different compositions and structures from the p-type region 112 and the n-type region 111 of the first sub-cell 110 . In any case, the composition and structure of each of the p-type region 141 and the n-type region 142 of the third sub-cell 140 are, for example, of the first sub-cell 110 in this specification. It may be selected from those described for the p-type region 112 and the n-type region 111.

In a bifacial multijunction photovoltaic device, the second/back electrode 102 must be translucent or transparent to allow transmission of light through the photoactive layer of the device. Therefore, the 2/back electrode 102 preferably has the same or similar composition and structure as that of the first/front electrode 101 . Accordingly, the composition and structure of the second/back electrode 102 may be selected from those described herein with respect to the first electrode 101 .

In addition, the surface 128 of the second sub-cell 120 adjacent to the third sub-cell 140 is the surface 127 of the second sub-cell 120 adjacent to the first sub-cell 110. It is preferred to have a surface profile identical to or similar to that of Accordingly, the surface profile of the surface 128 of the second sub-cell 120 adjacent to the third sub-cell 140 is the surface of the second sub-cell 120 adjacent to the first sub-cell 110. It is preferably the same as or similar to that described above with respect to (127).

Example

In the examples detailed below, a prefabricated n-type crystalline silicon heterojunction (SHJ) sub-cell was obtained, subjected to a custom chemical polish on the front/top surface, followed by blanket coating of a layer of ITO as an interconnect layer. (blanket coating) was applied. The front/top surface of the silicon heterojunction (SHJ) sub-cell was then cleaned using an oxygen plasma treatment.

For multijunction devices, a layer of n-type material was deposited on the front/top surface of a silicon heterojunction (SHJ) sub-cell using thermal evaporation. Subsequently, a layer of perovskite material of the formula MAPb(I _0.8 Br _0.2 ) ₃ , where MA is methylammonium (CH ₃ NH ₃ ⁺ ), was formed by spin coating deposition from solution. In this example, The solid precursors for the perovskite material were weighed and mixed together in a vial.Then this mixture was put into a glove box where the solvent was added.Then thin layers of p-type material were formed by spin coating from the solution. was deposited, and the cell was completed by depositing a patterned gold electrode by physical vapor deposition.

8 and 9 are I-V curves and calculations for an embodiment of an n-type crystalline silicon heterojunction (SHJ) sub-cell when measured as a monojunction device under simulated AM 1.5G (100 mW/cm2) solar irradiation. shows the device characteristics. The calculated power conversion efficiency (η) for each of these silicon heterojunction (SHJ) sub-cells is about 17%.

In comparison, FIGS. 10 and 11 show I-V curves and calculations for a multi-junction device including a perovskite-based sub-cell integrally integrated on an n-type crystalline silicon heterojunction (SHJ) sub-cell, respectively. shows the device characteristics. The calculated power conversion efficiencies (η) for these multi-junction type devices are 20.1% and 20.6%, a net gain of about 3% efficiency over the mono-junction type crystalline silicon heterojunction (SHJ) sub-cell.

Each of the foregoing items may be used alone or in combination with other items shown in the drawings or described in the description, and items referred to in the same section or in the same figure need not be used in combination with each other.

Moreover, although the present invention has been described with respect to preferred embodiments as described above, it should be understood that these embodiments are merely illustrative. Modifications and changes will occur to those skilled in the art with reference to the disclosure deemed to fall within the scope of the appended claims. For example, one skilled in the art will understand that while certain of the foregoing embodiments of the present invention are all directed to photovoltaic devices having a multi-junction type structure, aspects of the present invention require a layer of photoactive perovskite to be deposited on a relatively rough surface. It will be appreciated that the same can be applied to unijunction devices with As a further example, those skilled in the art will appreciate that while the foregoing embodiments of the present invention all relate to photovoltaic devices, aspects of the present invention are equally applicable to other optoelectronic devices. In this regard, the term "optoelectronic device" includes photovoltaic devices, photodiodes (including solar cells), phototransistors, photomultipliers, photoresistors, light emitting diodes, and the like. In particular, although a photoactive perovskite material is used as a light absorber/photosensitizer in the above embodiment, it may function as a light emitting material that later recombines and emits light by accepting charges, electrons and holes.

Claims (32)

A multijunction photovoltaic device that produces a net gain in power conversion efficiency in excess of the efficiency of a bottom silicon sub-cell in a unijunction structure, comprising:
a first sub-cell disposed on a second sub-cell;
The first sub-cell comprises an n-type region comprising one or more n-type layers, a p-type region comprising one or more p-type layers, and disposed between the n-type region and the p-type region, and the n-type region and a photoactive region comprising a layer of perovskite material, without open pores, forming a planar heterojunction with one or both of the p-type regions;
The perovskite material has the general formula (IA),
A _x A' _1-x B(X _y X' _1-y ) ₃ (IA)
where A is methylammonium cation (MA) (CH ₃ NH ₃ ⁺ ), formamidinium cation (FA) (HC(NH) ₂ ) ₂ ⁺ ), and ethyl ammonium cation (EA) (CH ₃ CH ₂ NH ₃ ⁺ ), A′ comprises one or more inorganic cations selected from Cs+, Rb+, Cu+, Pd+, Pt+, Ag+, Au+, Rh+, and Ru+, and B is Pb ²⁺ At least one divalent inorganic cation comprising, X is iodide, X' is bromide, 0 < x ≤ 1, 0 < y ≤ 1,
The second sub-cell comprises a silicon heterojunction (SHJ),
Multijunction photovoltaic devices. According to claim 1,
wherein the layer of perovskite material is disposed as a substantially continuous and conformal layer on a surface conformal to an adjacent surface of the second sub-cell.
Multijunction photovoltaic devices. According to claim 1 or 2,
further comprising an intermediate region disposed between and connecting the first sub-cell and the second sub-cell, wherein the intermediate region comprises one or more interconnection layers;
Multijunction photovoltaic devices. According to claim 3,
wherein each of the one or more interconnect layers comprises a transparent conductive material;
Multijunction photovoltaic devices. According to claim 3,
wherein the intermediate region comprises an interconnection layer made of indium tin oxide (ITO).
Multijunction photovoltaic devices. According to claim 5,
The layer of ITO has a thickness of 10 nm to 60 nm,
Multijunction photovoltaic devices. According to claim 1 or 2,
wherein the n-type region comprises an n-type layer comprising an inorganic n-type material;
Multijunction photovoltaic devices. According to claim 7,
The inorganic n-type material,
Oxides of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium, cadmium, or two of titanium, tin, zinc, niobium, tantalum, tungsten, indium, gallium, neodymium, palladium and cadmium oxides of one or more mixtures;
sulfides of cadmium, tin, copper, zinc or sulfides of mixtures of two or more of cadmium, tin, copper and zinc;
selenide of cadmium, zinc, indium, gallium or a mixture of two or more of cadmium, zinc, indium and gallium; and
selected from any one of tellurides of cadmium, zinc or tin, or tellurides of mixtures of two or more of cadmium, zinc and tin;
Multijunction photovoltaic devices. According to claim 7,
The n-type region comprises an n-type layer containing TiO ₂ ,
Multijunction photovoltaic devices. According to claim 1 or 2,
wherein the n-type region comprises an n-type layer comprising an organic n-type material;
Multijunction photovoltaic devices. According to claim 10,
The organic n-type material is fullerene or a fullerene derivative, perylene or a perylene derivative, or poly{[N,N0-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide ) -2,6-diyl] -alt-5,50- (2,20-bithiophene)} (P (NDI2OD-T2)),
Multijunction photovoltaic devices. According to claim 1 or 2,
wherein the p-type region comprises a p-type layer comprising an inorganic p-type material;
Multijunction photovoltaic devices. According to claim 12,
The inorganic p-type material,
oxides of nickel, vanadium, copper or molybdenum; and
selected from any one of CuI, CuBr, CuSCN, CuO, CuO or CIS;
Multijunction photovoltaic devices. According to claim 1 or 2,
wherein the p-type region comprises a p-type layer comprising an organic p-type material;
Multijunction photovoltaic devices. 15. The method of claim 14,
The organic p-type material is selected from any one of spiro-MeOTAD, P3HT, PCPDTBT, PVK, PEDOT-TMA, PEDOT: PSS,
Multijunction photovoltaic devices. According to claim 1 or 2,
the n-type region is adjacent to the second sub-cell;
Multijunction photovoltaic devices. According to claim 1 or 2,
Further comprising a first electrode and a second electrode,
the first sub-cell and the second sub-cell are disposed between the first electrode and the second electrode, the first sub-cell being in contact with the first electrode;
Multijunction photovoltaic devices. 18. The method of claim 17,
the first electrode contacts the p-type region of the first sub-cell;
Multijunction photovoltaic devices. 18. The method of claim 17,
wherein the first electrode comprises a transparent or translucent electrically conductive material;
Multijunction photovoltaic devices. 18. The method of claim 17,
The first electrode is made of a layer of indium tin oxide (ITO),
Multijunction photovoltaic devices. According to claim 1 or 2,
wherein the photoactive region of the first sub-cell comprises a layer of perovskite material having a band gap of 1.50 eV to 1.75 eV.
Multijunction photovoltaic devices. According to claim 1,
The perovskite material is FA _x Cs _1-x PbI _3-y Br _y ,
Multijunction photovoltaic devices. According to claim 1,
The perovskite material is MAPb (I _0.8 Br _0.2 ) ₃ ,
Multijunction photovoltaic devices. According to claim 1 or 2,
The second sub-cell includes a double-sided sub-cell, and the device further includes a third sub-cell disposed below the second sub-cell, the third sub-cell comprising a perovskite a photoactive region comprising a layer of material,
Multijunction photovoltaic devices. 25. The method of claim 24,
The photoactive region of the third sub-cell comprises a layer of perovskite material that is the same as or different from the perovskite material of the photoactive region of the first sub-cell.
Multijunction photovoltaic devices. 25. The method of claim 24,
wherein the first sub-cell has a normal structure and the third sub-cell has an inverted structure;
Multijunction photovoltaic devices. According to claim 3,
further comprising an additional intermediate region disposed between and connecting the third sub-cell and the second sub-cell, the additional intermediate region comprising one or more additional interconnection layers;
Multijunction photovoltaic devices. 28. The method of claim 27,
each of the one or more additional interconnection layers is made of a transparent conductive material;
Multijunction photovoltaic devices. 28. The method of claim 27,
the intermediate region comprises an additional interconnection layer made of indium tin oxide (ITO);
Multijunction photovoltaic devices. delete delete delete

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